1. Field of the Invention
This invention relates generally to chainless bicycles, and more particularly to a chainless bicycle having a dual drive shaft and floating drive train suspension system.
2. Brief Description of the Prior Art
Since the bicycle was first invented, it has gone through several stages of development. The first bicycles were rigid frames with pedals connected directly to the front wheel. Later bicycles were provided with a chain sprocket having pedals which was rotatably mounted on the frame and connected to a smaller gear sprocket mounted on the hub of the rear wheel by a chain. Three-speed bicycles were developed which had a lightweight frame with a pedal sprocket and a series of smaller sprockets at the rear wheel which allowed the cyclist to selectively change gear ratios by a lever and flexible cable.
The three-speed bicycles were replaced by ten-speed bicycles. The ten-speed bicycles had a lightweight frame and a pedal sprocket which had a series of laterally spaced drive sprockets of various diameter and a series of laterally spaced smaller sprockets at the rear wheel. The ten-speed bicycle had a first lever for switching the chain between the pedal sprockets and a second lever for switching the chain between the rear wheel sprockets. This allowed a wider range of gear ratio selections between various combinations of pedal sprockets and rear wheel sprockets. The chain was shifted from one pedal sprocket cog to another and from one cog of the rear wheel sprocket to another by a pair of devices known as a derailleur. The derailleur was a very delicate mechanism and required frequent adjustment and repair.
Another bicycle development was a bicycle known as a "BMX" bicycle. These bicycles were small and very rugged and were used in racing on rough terrain and specially designed obstacle courses or dirt tracks wherein the participants raced over hills, birms, mud, and a variety of obstacles and performed acrobatic maneuvers such as "jumps", "wheelies", and "handlebar stands." The sport of BMX racing led to the development of very strong lightweight metal alloy frames and wheel rims and high impact plastic wheel rims. The BMX bicycle was also driven by a pedal sprocket connected to the rear wheel sprocket by a chain and usually had a low gear for torque and may or may not have had a selective gear ratio.
Recently, a new type of bicycle known as the "mountain bike" has been developed. The "mountain bike" combines the features of the ten-speed bicycle and the BMX bicycle. The "mountain bike" is used on rough mountain terrain, hiking trails, and cross country riding, wherein the cyclist rides on rocks, grass, mud, etc. The mountain bike has a very strong lightweight metal alloy frame and wheel rims and a wide selection of gear ratios, however, the mountain bike is also driven by a pedal sprocket connected to the rear wheel sprocket by a chain and has a delicate derailleur device.
Thus, the trend has been toward increasingly rugged all-terrain bicycles with a wide range of gear ratios which are ridden on very rough terrain and subjected to much abuse. Although the frames, wheels, rims, and sprockets are very strong and can withstand the abuse, the chain drive and delicate gear selection mechanisms remain the weakest link in the system. The chain is exposed to water and abrasives, such as dirt, sand, and mud. If not properly maintained, a chain can wear out in only 500 miles. A worn chain can jump off gear teeth and cause an accident.
Others have attempted to overcome these problems and provide more efficient drive mechanisms by replacing the chain drive with a single or dual drive shaft. There are several patents which disclose various chainless bicycles having single or dual drive shafts. However, the pedal drive gear and rear wheel of the bicycle are rigidly fixed to the frame of the bicycle. This rigidly fixed arrangement is unsatisfactory, since the modern bicycle is subjected to a great deal of jarring, vibration, and impact, and the rigidly fixed gears would soon become misaligned and, damaged.
Fryer, U.S. Pat. No. 506,685 discloses a dual drive shaft driven bicycle which has a double faced bevel gear which is moved laterally to engage either of two pinion gears or an intermediate neutral position between the bevel gears by an upstanding fulcrum lever which allows the bicycle to coast without pedaling. The drive shafts are rotatably secured to the frame of the bicycle. Thus, the drive shafts are rigidly mounted to the frame and when the gears are engaged, the pedals will constantly rotate unless they are manually disengaged by the upstanding fulcrum lever. The fulcrum lever also presents a safety hazard if the cyclist should slip or fall.
Harden, U.S. Pat. No. 616,571 discloses a dual drive shaft driven bicycle which has a pair of bevel gears at each side of the crank hanger which are constantly engaged with two pinion gears at the forward end of drive shafts. The drive shafts extend rotatably through tubular bottom run members which are rigidly secured to the crank hanger at their forward end and to the rear stays at their rearward end. The crank hanger, bottom run tubes and rear stays form an integral rigid portion of the frame. The power is applied equally on both sides of the rear wheel and there is no provision for selective gear ratios or for a neutral gear for coasting without pedaling, and the drive shafts are rigidly mounted to the frame.
Jocelyn, U.S. Pat. No. 620,929 discloses a dual drive shaft driven bicycle which has a double faced bevel gear which is constantly engaged with two pinion gears at the forward end of drive shafts. The pedal gear box is joined to the rear wheel gear box by a pair of laterally spaced tubular tie bars in which the drive shafts are journalled. A pair of bevel gears are slidably mounted on the axle of the rear wheel hub and are moved laterally to engage either of two pinion gears at the rear end of the drive shafts or an intermediate neutral position between the bevel gears to allow the bicycle to coast without pedaling. The gear boxes and tie bars are formed in an upper half and a lower half which ar joined together to surround the drive shafts and gears, and form an integral rigid portion of the frame. The pinion gears are provided with a polygonal socket and the ends of the drive shafts are provided with a mating polygonal end which is received in the pinion gear sockets. Thus, the drive shafts move axially relative to the pinion gears to compensate for slight yielding of the bicycle frame in use.
Schoenthal, U.S. Pat. No. 653,968 discloses a single drive shaft driven bicycle which has a bevel gear at one side of the crank hanger which is constantly engaged with a pinion gear at the forward end of a drive shaft. The drive shaft extends rotatably through a tubular member of a frame component having a pair of parallel support tubes above and below the drive shaft tube which are rigidly secured to the crank hanger at their forward end and to a D-shaped bracket at their rearward end which supports the rear wheel and the rear stays. The frame component which carries the drive shaft forms an integral rigid portion of the frame. The power is applied equally only on one side of the rear wheel and there is no provision for selective gear ratios or for coasting without pedaling.
Brown et al, U.S. Pat. No. 744,038 discloses a single drive shaft driven bicycle which has a bevel gear at one side of the crank hanger which is constantly engaged with a pinion gear at the forward end of a drive shaft. The drive shaft extends rotatably through a tubular member of a frame component which is rigidly secured to the crank hanger the forward end and to a pinion gear housing at the rearward end which supports the rear wheel and the rear stays. The frame component which carries the drive shaft forms an integral rigid portion of the frame. The power is applied only on one side of the rear wheel and there is no provision for selective gear ratios or for coasting without pedaling.
Hussey, U.S. Pat. No. 2,378,634 discloses a single drive shaft driven bicycle which has a circular face gear in the crank hanger which is dished outwardly from the hub and has three concentric rings of gear teeth of different diameters. The drive shaft extends rotatably through a tubular member of a frame component which is rigidly secured to the crank hanger the forward end and to a bevel gear housing at the rearward end which supports the rear forks of the frame. A pinion gear slidably mounted on the forward end of the drive shaft slides axially on the drive shaft to engage selective ones of the rings of gear teeth on the face gear to change gears or to be positioned in a neutral position. The tubular component which carries the drive shaft forms an integral rigid portion of the frame.
Mendoza, U.S. Pat. No. 3,861,715 discloses a single drive shaft driven bicycle which has a large diameter crown gear at one side of the crank hanger. The drive shaft extends rotatably through a tubular member of a frame component which is rigidly secured t the crank hanger the forward end and to a gear housing at the rearward end which supports the rear forks of the frame. A pinion gear secured on the forward end of the drive shaft is engaged with the gear teeth of the crown gear and a set of conical gears at the rear of the drive shaft are connected to a free-wheeling mechanism in the hub of the rear wheel to allow coasting without pedaling. There is no provision for changing gears and the tubular component which carries the drive shaft forms an integral rigid portion of the frame.
Conventional chain driven bicycles have a rigid frame comprising a downtube, seat tube, and a pair of horizontal chain stays which are secured to a crank hanger which contains the pedal assembly. The chain stays are rods or tubes which extend horizontally rearward and have a slotted bracket or dropout secured to the rear ends into which the rear wheel is mounted. The frame also includes a pair of seat stays which are rigid tubular members secured at their top ends to the seat tube and to the rear wheel dropouts at their bottom ends. The seat tube, chain stays, and seat stays form the rigid rear triangle of the bicycle frame.
The chainless, or drive shaft driven, bicycles of the prior art replace one or both horizontal chain stays with a hollow tube which contains the drive shaft. However, these tubular members are rigidly secured to the crank hanger and have a rear wheel bracket or gear box at their rearward ends, and a pair of rigid seat stays or tubular braces are secured angularly between the seat tube and the rear wheel bracket or gear boxes. Thus, these chainless bicycles also provide a rigid rear triangle for the bicycle frame. This rigid frame construction subjects the gear drive train and gear mechanisms to vibration, jarring, and impact, and the rigidly mounted gears would soon become misaligned and damaged.
The present invention is distinguished over the prior art in general, and these patents in particular by a chainless bicycle having a frame with a top bar, steering tube, front forks, front wheel, handlebar assembly, seat assembly, seat tube, and front downtube. The seat tube and front downtube extend angularly downwardly and are connected at their lower ends to a special crank hanger which pivotally supports a pedal gear box containing drive gears connected to the pedal arms. A pair of hollow support tubes connected to the pedal gear box extend rearwardly to a rear wheel gear box at each side of the rear wheel. A drive shaft is rotatably carried in each support tube and each has a bevel gear at the front end selectively engaged with the drive gears in the pedal gear box and a bevel gear at the rear end inside the rear wheel gear box. The hub of the rear wheel has a drive and braking mechanism which is connected to bevel gears at each side. The gears of the rear wheel hub are received in toothed engagement with the bevel gears in the rear wheel gear boxes. A pair of fluid shock absorbers are mounted between the rear wheel gear boxes and the seat tube. Thus, the chainless bicycle has a "floating" drive train and rear wheel suspension system to isolate the gear drive train from jarring, vibration, and impact, and prevent the gear drive members from becoming misaligned and damaged.